1. Field of the Invention
The present invention relates to a dielectric barrier discharge apparatus for perfluorocompound (PFC) abatement and a dielectric barrier discharge module composed of a plurality of dielectric barrier discharge apparatuses.
2. Description of the Prior Art
Since the 1992 United Nations Framework Convention on Climate Change (UNFCCC), reduction of the emission rates of processed gases believed to contribute to global warming has become a worldwide issue. Also, according to the agreement of the xe2x80x9cTokyo Conferencexe2x80x9d, each participating country must improve the emission rates of released industrial gases, such as CO2, CH4, NO, HFC, and PFCs, to a set of predetermined levels. Semiconductor associations of the Unite States, Japan, and Europe have promised to decrease the emission rates of PFCs to 90% of the 1995 level before 2010. It has become extremely important for industry to reduce the emission rates of perfluorocompounds.
In U.S. Pat. No. 5,387,775, M. Kang proposes a plasma reaction chamber, which comprises a ceramic plate acting as a dielectric barrier and a conductive liquid acting as a grounding electrode. Applying the conductive liquid can abate the hydrofluoric and hydrocyanic acid produced from the plasma reaction.
In U.S. Pat. No. 5,637,279, M. M. Besen and D. K. Smith propose a chamber to produce ozone and reacting gases, and a system thereof. The apparatus comprises a plasma reacting chamber assembled by welding, and cooling channels. Cooling liquid is introduced to cool the electrodes, and the plasma reacting chamber is modular.
In U.S. Pat. No. 5,932,180, the continuous application of U.S. Pat. No. 5,932,180, X. Zhang et al propose a method to process the surface of the plate electrodes, wherein wolfram (W) is applied.
In U.S. Pat. No. 6,007,785, H. T. Liou proposes a high efficiency ozone-generating apparatus. The Compressure of inflow gases is maintained at less than 1 atm.
In U.S. Pat. No. 6,045,761, A. Bill et al propose a discharge reactor and an application thereof. The apparatus comprises an apertured dielectric barrier, wherein the surfaces of the apertures are coated with a metallic oxide to enhance the chemical reaction of the plasma in the apertures.
In U.S. Pat. No. 6,146,599, R. R. Ruan et al propose a dielectric barrier discharge system and a method to abate the toxic compounds in fluids, wherein a modular dielectric barrier discharge system is applied.
In U.S. Pat. No. 6,245,299, J. Shilon et al propose a modular dielectric barrier discharge system for pollutant abatement. Each dielectric barrier discharge chamber is connected to an independent power supply. The process gases are introduced to one of the dielectric barrier discharge chambers and then to another. Each of the dielectric barrier discharge chambers is provided with power with a voltage range from 300V to 100 kV and an RF frequency range from 10 kHz to 3 MHz. Each of the dielectric barrier discharge chambers comprises inner and outer dielectric barriers arranged to provide a gap for the passage of gases, and plasma generated in the gap. The dielectric barrier is aluminum oxide or quartz.
A purpose of the present invention is to provide an innovative dielectric barrier discharge apparatus and the module thereof, wherein dielectric barrier discharge plasma (DBD plasma) is applied to enhance the destruction and removal of perfluorocompound.
Another purpose of the present invention is to provide a dielectric barrier discharge apparatus impervious to corrosive gases, such as hydrofluoric acid or fluorine. Furthermore, the apparatus of the present invention is convenient to assemble.
A further purpose of the present invention is to provide a module comprising a plurality of dielectric barrier discharge apparatuses, wherein the capacity of perfluorocompound treatment is adjustable, according to the flow rate of perfluorocompound gases.
The dielectric barrier discharge apparatus of the present invention comprises a housing, a first dielectric tube disposed in the housing, a second dielectric tube disposed in the first dielectric tube, and at least one electrode disposed in the housing. A first cooling gas passage is formed between the housing and the first dielectric tube, a PFC passage is formed between the first and second dielectric tubes, and a second cooling gas passage connected to the first cooling gas passage is formed in the second dielectric tube. While the applied voltage for the electrodes is greater than a breakdown voltage, high energy electrons generated in the PFC passage can ionize or dissociate the PFCs to be removed. The first and second dielectric tubes are ceramic, and are impervious to corrosive gases, such as hydrofluoric acid or fluorine transformed from the perfluorocompound. The first and second cooling gas passages are used to introduce cooling gas to cool the electrodes.